CTLA-4 (cytotoxic T-lymphocyte-associated antigen-4) or CD152 is an inhibitory checkpoint-marker that competes with CD28, binding CD80/CD86 on leukemic blasts and it has been shown to be upregulated in primary AML samples and poor prognosis is associated with it, especially when expressed concurrently with PD-L1 and PD-L2 on leukemic cells [184]. Here, CD80 is linked to acute myeloid leukemia.